Wild aquatic birds are considered to be the natural reservoir for influenza A viruses, and previous studies have focused mainly on species in the orders Anseriformes and Charadriiformes. In this study, we surveyed a larger spectrum of potential hosts belonging to 10 avian orders. Cloacal swabs (n=1,044) from 72 free-living bird species, were analysed by reverse transcription-polymerase chain reaction for the presence of avian influenza virus. Only two Mediterranean Gulls (Larus melanocephalus) tested positive; one of these viruses was identified as an H9N2 subtype. The absence of infection among passerine birds supports the idea that the prevalence of avian influenza virus infection in terrestrial species is low.